First MAX- DOAS results of the SO292-2 cruise across the Pacific in June/July 2022: Nouméa (New-Caledonia) to Dutch Harbor (Alaska, USA)

Transit cruises of German research vessels across oceans provide a unique platform for MAX-DOAS measurements of atmospheric trace gases such as nitrogen dioxide (NO2), formaldehyde (HCHO) and sulphur dioxide (SO2). The Deep Blue/PORD campaign took place from 24 June to 21 July 2022. During that period the research vessel SONNE was crossing the Pacific in meridional direction from 22° S to 54° N in an area that is typically used as reference for satellite data due to its large distance from anthropogenic emission sources.In this study we focus on three trace gases: NO2 columns provide information on the meridional distribution of stratospheric NO2 as well as the distribution of tropospheric background NO2 above the marine boundary layer. For the analysis, high signal “peaks” that only last a short time are filtered as they most likely originate from the ship exhaust. First results show a minimum of total NO2 columns between the equator and about 15° N. HCHO and SO2 mainly appear as plumes from nearby islands and/or volcanoes in the Solomon Sea, where biogenic and volcanic activities are naturally high. In combination with the onboard instrumentation (Ceilometer, Pyranometer and a cloud camera) this data set provides a detailed description of the atmosphere along the cruise track.